Is interest in 9/11 waning or changing course?

Nearly 3,000 people killed. A nation's collective psyche decimated. Two costly, protracted wars. And fallout affecting everything from air travel to privacy.

The Sept. 11 terrorist attacks left deep, lasting scars that will be acknowledged Wednesday in commemorations at Ground Zero in New York, the Pentagon and Shanksville, Pa., the sites where terrorists crashed four hijacked commercial airliners. But on the 12th anniversary of 9/11, there are signs of a gradual desensitization to the tragedy's once-piercing wounds.

Near Madison, Wis., the Tumbledown Trails Golf Course offered a "12th anniversary of 9/11" special: a nine-round golf game for $9.11 or 18 rounds for $19.11. That was until course owner Marc Watts received death threats and apologized after a social media backlash that required protection from sheriff's deputies. "We're a little hurt by the fact that people are putting such a negative context on this," Watts said.

On the eve of New York's mayoral primary election, 9/11 morphed from sacred day to political football after Police Commissioner Ray Kelly accused candidates of being soft on terrorism.

In London, a sculpture by New York artist Miya Ando made from twin towers debris in honor of 67 Britons killed on 9/11 has languished in storage for two years, unable to find a permanent home. "In my lifetime, it's the single most influential tragedy and saddest thing I've experienced,'' Ando, 34, told USA TODAY. "I hope (Londoners) find a home for it."

Wednesday marks the fifth year since Congress declared 9/11 a National Day of Service and Remembrance, a designation that was news to about a quarter of Americans in a Horizon Consumer Science survey.

Yet the public's overall interest in 9/11 and honoring those who died doesn't appear to be waning, just shifting, as people commemorate an anniversary once steeped in sadness and anxiety in a variety of ways. Some tributes are attached to positive, uplifting emotions, such as volunteering at a soup kitchen or doing some other charitable act.

Though two in three Americans say they've "moved on" from the horror of Sept. 11, nearly the same percentage say they will mark 9/11 in a formal or informal manner such as attending a memorial or saying a prayer, according to an American Pulse survey conducted for USA TODAY.

David Paine, co-founder of the non-profit 9/11 Day Observance, sees each anniversary as a reminder for people to perform a good deed to honor those who perished that day.

"Our country will always remember Sept. 11 victims," he says, but how it does that "is evolving."

His hope is that Sept. 11 will turn into a day that means national service, as well as a day to pay homage to first responders.

"There's a Veterans Day for members of the military, and there isn't a day when people honor first responders," he says.

Even with passing time, a rising number of people pledge on his group's 911day.org website to do a good act.

"This is growing at a grass-roots level more than in the 12 years that I've been working on this," Paine says.

Americans are more apt to keep up the commemorations of the lives lost on Sept. 11, than, say, the Pearl Harbor attack on Dec. 7, 1941, says Edward Berenson, a New York University history professor who was part of a research project on the New York Sept. 11 memorial.

"We now live in a culture of memorialization," he says. "We've invented ways of keeping memories alive that didn't exist in the aftermath of Pearl Harbor."

Social media have "had a big impact" on how we do that, Berenson says. They facilitate sharing thoughts and images and allow "people who were affected by it to be in touch with each other and to deepen those contacts."

Traditional media also keep the memory of Sept. 11 vivid. "We can all picture the smoking top of the buildings,'' Berenson says. "We will see those images again and again."

As for comparing the Sept. 11 attack to Pearl Harbor, there are other major differences:

For instance, "Pearl Harbor got overshadowed by all the other events of the second World War," he says, pointing out the "magnitude" of the Holocaust and the atomic bombings. "There was extraordinary, unprecedented violence" throughout that war.

As for Sept. 11, "it is impossible to predict" how long people will honor the heroes and memorialize the victims, he says.

"The staying power will depend on things that we can't see in the next 10 or 20 years," he says. "We can all hope that there is not an equivalent event or worse event that will overshadow it or make it seem like the first in a terrible series of things."

If there are no other large-scale events like that, "it's likely that Sept. 11 will be a landmark (in our) collective memory," he says. "It's going to last."